Method of electroforming rectifier elements



Patented Dec. 28, 1948 UNITED STATES PATENT OFFICE METHOD OF ELECTROFOBMING RECTIFIER ELEMENTS Murray I. Stateman, Brooklyn, N. Y., assignmto Federal Telephone and Radio Corporation, New York, N. 1., a corporation of Delaware No Darin. Application April 9, 19515,

Serial No. 587,422

mation process can be performed by the use oi direct or alternating current.

It has been observed before that the performing of the electroformation process in somewhat humid air is of beneficial yet still not satisfying influence to the electroiorm'lng process and it is also known that the use of a. higher voltage during the electroforming process is very much desired.

Realizing the beneficial effect of providing moisture to the rectifier element before the elee troforming process takes place, it has been proposed before to dip the rectifier element in wat it at a temperature range of 160 to 212 R, or go soak the rectifier element in water at room telnperature. Although these methods oi additiu moisture resulted in the advantage to achieve a higher electroforming voltage there was a tendency to apply a still higher voltage as achieved by the above mentioned proposal.

It is, therefore, the main object of the present invention to provide a method according to which a voltage higher than it has been possible up to the present time is used in the elcctroiormi na process.

It is a further object of the present invention to provide a method according to which the time of the electroforming process is shortened.

With these and other objects in view, the pres ent invention will be clearly understood from the following description.

According to the method of the present invention, the rectifier elements are first formed in the usual manner by providing, a semi-conductor layer on a base plate and then covering the semiconductor layer with a counter-electrode layer. The usual electroiorming process which follows is performed according to the present invention by moistening the rectifier elements before the electroforming process is started. This moistening can be achieved by means of steam which condenses on the cold rectifier element or by rinsing the cold rectifier element in hot water, preferably at a temperature of 40 C. to 80 C. It has been found that still better results are achieved iii 2 if both, namely, first the steaming and then the rinsing in hot water within the above mentioned temperature range is used upon the rectifier element before the electroforming process is performed. 'By exposing the rectifier element to the mentioned treatment the latter is moist when the electroiorming process is started. The steaming treatment of the rectifier element is done for a preferred time of about 15 seconds whereas the rinsing treatment canbe done in any shorter or longer time.

The present method of moistening the rectifier element before the electroforming is performed allows the usual voltage of 20 to 25 volts now used in the electroforming process to be increased to about 30 volts and at the same time the time for the electroforming process is reduced from the usual four hours to about one hour.

A still further improved method according to the present invention appears in first exposing the rectifier elements to the electroforming proceat at a voltage of up to 25 volts which will take about a half of an hour and then interrupting this eiectroforming process, exposing the partially electroformed rectifier element to the above mentioned moistening treatment by steaming or rins= ing in hot water, or both, and then continuing the electroforming process of the rectifier element which is moist from the previous treatment until a voltage of about 30 volts is reached in the continued electroforming process. The voltage of about 30 volts is reached in the continued electroiorming process within about five minutes, thereby reducing the usual electroforming process from about four hours to about thirty-five minutes for both periods of electroforming. Thus, it appears that the improved method shows further advantages over the first mentioned.

By performing the electroforming process according to the present invention high voltage rectifier discs may be electroiormed at a higher voltage than used before in a shorter time than it was possible and yielding high quality characteristics for' the rectifier elements.

While I have disclosed the principles of my invention in connection with several difierent embodiments, it will be understood that these embodiments are given by way of example only and. not as limiting the scope of the invention as set forth in the objects and the appended claims.

What I claim is:

1. In the manufacture of selenium rectifier elements, the steps that comprise selecting elements comprising a base plate carrying a selenium layer and a counterelectrode and electroforming said elements at a voltage up to about 25 volts for about one-half hour, interrupting the electroforming and moistening the elements, and thereafter electroforming these elements while still moist for a period of about five minutes using a progressively increasing voltage until a level of about 30 volts is reached.

2. The process of claim 1 wherein the moistening of the elements is performed by exposing the cold elements to steam.

3. The process of claim 1 wherein the moistening of the elements is performed by rinsing the elements in hot water.

4. The process of claim 1 wherein the moistening of the elements is performed by rinsing the elements in hot water at 2, temperature of to to 4 5. The process of claim 1 wherein the moistening of the elements is performed by exposing the cold elements to steam and thereafter rinsing said elements in hot water at a temperature of 40 to 80 C.

MURRAY J. STA'I'EMAN.

REFERENCES CITED The following references are of reeordin the 2,395,259 Ellis et a] Feb. 19, 1946 

